Wireless access systems have been widely deployed to provide various types of communication services such as voice or data. In general, a wireless access system is a multiple access system that supports communication of multiple users by sharing available system resources (a bandwidth, transmission power, etc.) among them. For example, multiple access systems include a Code Division Multiple Access (CDMA) system, a Frequency Division Multiple Access (FDMA) system, a Time Division Multiple Access (TDMA) system, an Orthogonal Frequency Division Multiple Access (OFDMA) system, a Single Carrier Frequency Division Multiple Access (SC-FDMA) system, and the like.
As more communication devices require greater communication capacity, the necessity for mobile broadband communication which is enhanced compared to a legacy radio access technology is emerging. And, massive MTC (Machine Type Communication), which provides various services at any time and any place by connecting a plurality of devices and objects, is also one of main issues to be considered in next generation communication. Moreover, discussion on designing a communication system considering a service/UE sensitive to reliability and latency is in progress.
In particular, discussion on introducing a next generation wireless access technology considering the enhanced mobile broadband communication, the massive MTC, the URLLC (Ultra-Reliable and Low Latency Communication), and the like is in progress. In the present invention, for clarity, the next generation wireless access technology is referred to as NR.